Modern thermal print heads have achieved levels of resolution based upon integrated circuit construction techniques which can locate a great number of individual heating elements in close proximity to each other. This advantage of resolution creates a limitation on the total span of the print head due to the possibility of faults occurring in the semiconductor, both in the manufacturing process and later in the printing application. Larger print spans have been achieved by aligning two or more smaller print heads to achieve the wider span. Also, due to the resolution achieved, relatively small misalignment between such multiple print heads are easily noticed in the resulting printed product. Even misalignments of as little as one pixel can be visually determined.
The construction and accuracy of multiple thermal print head alignment is further challenged by the need to substantially squeeze the print media against the thermal print head to provide good thermal conductivity.